1. Field of the Invention
This invention relates to disk drive suspensions comprising load beams and flexures in which the flexure tongue is limited in its travel by a limiter structure. More particularly, the invention relates to the snap-in connection of the flexure tongue-borne limiter structure to the load beam in a movement requiring only the pressing together of the load beam and flexure. Relative longitudinal movement of the flexure or flexure tongue and the load beam, usually required with flexure tongue-borne limiter structures that insert into the load beam with a longitudinal axial movement, is obviated, with resultant increased production rates and reduced incidence of defects.
In the invention, a snap-fit disk drive suspension assembly is provided comprising a load beam having a slot and secured to the load beam a flexure having a cantilevered tongue opposing the load beam and adapted to carry a slider. The invention structure is suitably formed on the tongue and sized to limit excursions of the tongue relative to the load beam. The limiter structure comprises a normally upright, resilient tab offset from a cooperating slot. The tab, typically carried by the flexure is similarly resilient so as to be deflectable bodily by the load beam in which the cooperating slot is formed until the slot registers with the tab. The limiter tab thus snaps into the slot in a deflected condition and immediately returns to an upright condition thereby engaging the tab with the load beam at the slot edge margin. The so-fixed limiter structure thus limits the flexure tongue excursions, is placed in position without relative longitudinal axial displacement of the load beam and flexure, and once so snapped into place is engaged there permanently.
2. Related Art
Limiter structures or more simply limiters are mechanical devices that block unwanted movement of a flexure tongue as it carries the suspension slider, usually by blocking undue movement with a structure supported by the flexure, the load beam or both. Workers in the art of limiter structures have attempted to meet progressively more difficult requirements for advanced disk drive suspensions. Initially, the main criterion was shock resistance, then load/unload capability became important. In a suspension shock resistance is the ability of the suspension to limit the angular stroke and/or the displacement of the flexure relative to the load beam so that the slider does not damage the disk when the lift off shock threshold is surpassed. In cases where the slider design permits, in the simplest terms, this means that the suspension does not allow the slider to lift off the disk, thus controlling the slider movement directly. But, as the shock threshold requirement increases, the slider will eventually be lifted off the disk during a shock event. Thus, the problem becomes one of controlling the slider motion during the time the slider is no longer in contact with the disk. In this context, non-contact of the slider with the disk refers to the slider being more than a few times farther separated from the disk than it is in the steady-state flying condition. During flying, the slider may be from less than one microinch to several microinches from the disk; this is considered to be in contact. Not in contact is a separation of 100 microinches or more, possibly up to a few thousandths of an inch.
During the time the slider is not in disk contact, the slider motion is slightly restrained by the action of the flexure and the load beam acting on the mass of the slider. Since, however, the slider is greatly energized by a shock event, the soft flexure and load beam springing is unable to completely control the slider motion.
In load and unload cycles, the load beam and flexure are further used in a reverse role, i.e. to pull the slider away from the disk instead of holding it against the disk.
The two requirements of shock resistance and load/unload cycling have been addressed in a variety of load beam and flexure designs, e.g. U.S. Pat. No. 5,771,136; U.S. Pat. No. 5,526,205; and U.S. Pat. No. 5,570,249. In general, the prior art has emphasized solving either the shock problem or the load/unload cycle. Where shock resistance is the primary consideration, limiters have been proposed that contact the flexure near the center of mass of the slider, or if that is not possible, contacts the flexure on both left and right sides on a transverse line that crosses through the center of mass of the slider or near to it. Where load/unload cycling is the primary consideration, the preferred location of the limiter is near the leading edge of the slider because then the limiter restricts the ability of the nose to drop to far below the correct attitude, and this ensures that the slider will load and unload in the nose-up (leading edge-up) condition.
A difficulty with both prior art designs that give primacy to shock resistance and those that give primacy to load/unload cycling is the excessive cost of executing the design in a production environment relative to the benefit gained. Cost elements include the cost of the material to create the feature, the labor required, and the reduced yield realized if the feature has a yield impact. In the design of flexure limiters, many apparently effective designs require an interleaving of the flexure and load beam at the welding-fixture-loading step of the manufacturing process. That is, the interfitting male and female parts must be shifted, usually on their longitudinal axes, for there to be interfittment and engagement. This interfittment, given the tiny parts and the barely visible, even with magnification, zone of interfittment implicates serious labor cost increases and, because of the difficulty involved in the process, significant yield cost impact.
Thus, manufacturing engineers must take into account the small, e.g. thumbnail, size of the parts involved, the typical availability of both the load beam and the flexure only on separate frets of 5 to 10 pieces per fret, and bulkiness of the fixture that prevents the operator from readily using a microscope to aid the operator in correctly loading and interleaving these tiny parts. In the event of misloaded or misinterleaved parts, the limiter feature is not assembled correctly or it may be damaged during assembly. In either case there is an impact on device yield.
In a manufacturing cycle paced by the required welding time, the operator usually has forty seconds to load fixtures with twenty assemblies of three components each to keep up with the laser welding machine. A limiter product design that requires the operator to slow down to load correctly is more expensive to produce because the operator cannot keep up with the machine. The presence of these manufacturing problems generally typifies the devices of the above and like patented devices.
It is an object therefore, to provide an improved limiter in a disk drive assembly. It is another object to provide a disk drive suspension that is readily assembled, including interengaged limiter.
It is a particular object to assemble a disk drive suspension load beam and flexure by merely pressing together of the load beam and flexure wherein their relatively offset, but cooperating tab and slot structure defines the limiter.
Further objects include forming a flexure or load beam having a normally upright, resilient limiter structure that is deflectable, forming then thew load beam or flexure to a limiter structure receiving slot that is offset from the normally upright limiter structure, but that receives the limiter structure upon deflection of the structure as by the load beam closing on the flexure, the slot offset causing the received limiter structure to engage the slot edge margin when upright, or nondeflected, the resilience of the limiter structure enabling a snap-back of the limiter structure to its normal upright orientation, in which orientation the limiter structure cannot escape the slot.
Specifically, the limiter structure. typically comprises a flexure tongue-carried tab that will enter the load beam slot in a deflected condition, but return to an undeflected condition once the force of the load beam on the tab is relieved by the tab being into the slot. In the undeflected or upright condition the load beam slot continues offset relative to the tab, but the tab is now in a portion of the slot that enables the return of the tab to its upright, undeflected position. The tab and slot shapes are complementary to form a hooked engagement when the tab is upright within the slot. There is no interleaving by relative longitudinal shifting of the parts, rather the parts interfit when the tab and slot coincide, and the relative shapes preclude separation once interfitted.
The invention thus provides a limiter design that engages in a one-way action; it snaps together. By providing tabs on the flexure that snap over mating surfaces on the load beam, or vice versa, a disk drive configuration is realized that is top-loadable. That is, the unassembled parts are loaded vertically in sequence onto a weld fixture with out interleaving, and then guided into position with guide pins as is done with a suspension assembly that does not have a limiter feature. The difference is that with this invention, the parts can be simultaneously provided with a limiter structure with no assembly complications, as the limiter tabs will find the slots as the vertical stack is pressed together.
Accordingly, the invention provides a snap-fit disk drive suspension comprising a load beam and secured to the load beam a flexure having a cantilevered tongue opposing the load beam and adapted to carry a slider, a limiter comprising a cooperating slot and tab structure defined by said flexure tongue and load beam to limit excursions of the tongue relative to the load beam, the limiter comprising a normally upright, resilient tab offset from the slot and adapted to snap into the slot in tongue excursion limiting relation without relative axial displacement of the load beam and flexure.
In this and like embodiments, typically the tab is normally generally upright, the tab being resiliently deflectable to be received in the slot and return to the generally upright condition upon being received in the slot, the resilient tab in its upright condition is offset from said slot, said slot being arranged to receive said tab in its deflected condition and to retain said tab in its normal upright condition when engaged with the opposing load beam, the load beam slot being offset from the tab in its upright condition, the slot being arranged to receive the tab in its deflected condition and to retain the tab in its normal upright condition, the tab resiliently returning to its the upright condition upon being received in the slot, whereby excursions of the tongue from the load beam are limited by the engagement of the tab with the load beam, the tongue defines the tab and the load beam defines the slot, the tab being sufficiently resilient to snap to its upright condition upon reception in the load beam slot, or the tongue defines a plurality of the tabs, with the load beam defining a slot for each tab.
In a further embodiment, the invention provides a snap-fit disk drive suspension comprising a load beam and a flexure, the flexure having a tongue, the flexure tongue being limited to a predetermined travel excursion relative to the load beam by a normally upright limiter structure disposed at an angle of about 68 to 88 degrees relative to the flexure, the limiter structure having an inner end fixed to the flexure and a free outer end deflectable laterally relative to the inner end between undeflected and deflected conditions, the load beam having an opening offset from the limiter structure inner end and arranged to pass the limiter structure outer end through the load beam in its deflected but not its undeflected condition, the load beam opening having a surrounding edge margin, the limiter structure being resilient to return to its the undeflected condition upon passage of its the outer end through the load beam opening, the limiter structure outer end being shaped to engage the load beam opening edge margin in the undeflected condition of the limiter structure outer end responsive to the predetermined travel excursion of the flexure tongue.
In this and like embodiments, typically, the load beam and flexure each comprise a spring steel, the flexure, flexure tongue and limiter structure are integrally formed with each other from a common piece of spring steel, the flexure tongue defines a pair of limiter structures, the load beam defining a pair of the openings respectively offset from the limiter structures inner ends and arranged to receive the pair of limiter structures in flexure tongue travel excursion limiting relation, the flexure tongue has a proximate end fixed to the flexure and a free distal end, the limiter structure being fixed to the flexure tongue between its the proximate and distal ends, the flexure tongue defines a pair of the limiter structures, the load beam defines a pair of the openings, and the limiter structures are fixed to the flexure tongue intermediate its the proximate and distal ends, the limiter structures in the pair are laterally opposed across a portion of the flexure tongue intermediate its the proximate and distal ends, the flexure tongue has a proximate end fixed to the flexure and a free distal end, the limiter structure being fixed to the flexure tongue at its the distal end, the load beam defining the offset opening relative to distal end fixed limiter structure, the flexure tongue further defines intermediate its proximate and distal ends a pair of limiter structures, the load beam defining a pair of further openings offset relative to the pair of limiter structures for passage of the pair of the limiter structures only in their deflected condition and engagement only in their undeflected condition, and the distal end limiter structure is a first limiter structure, the intermediate limiter structures are second and third limiter structures and in which the flexure tongue further defines at its the proximate end a fourth limiter structure, the load beam defining a further opening offset relative to the fourth limiter structure for passage of the fourth limiter structure only in its deflected condition.
In a further embodiment, the invention provides a snap-fit disk drive suspension comprising axially aligned a load beam and a flexure having a frame attached to the load beam, the flexure having a tongue extending centrally of the frame in load beam attachment free relation, the flexure tongue being limited to a predetermined travel excursion relative to the load beam by a limiter structure having an inner end fixed to the flexure and a free outer end deflectable laterally relative to the inner end between undeflected and deflected conditions, the load beam having an opening offset from the limiter structure inner end, the load beam opening having a surrounding edge margin, the limiter structure resiliently returning to its the undeflected condition upon passage of its the outer end through the load beam opening, the limiter structure outer end being generally hook-shaped to pass the load beam opening in the deflected condition of the limiter structure outer end and to engage the load beam edge margin in the undeflected condition of the limiter structure outer end responsive to the predetermined travel excursion of the flexure tongue.
In yet another embodiment, the invention provides a snap-fit disk drive suspension comprising a load beam and a flexure having a flexure tongue, the flexure tongue having left and right edges and defining a laterally opposed pair of left and right limiter structures extending along the flexure tongue edges generally in parallel with the longitudinal axis of the flexure tongue and adapted to be sprung outward from the flexure tongue edges responsive to bodily contact with the load beam, the load beam defining a pair of the openings respectively offset laterally outward from the limiter structures inner ends and arranged to receive the pair of limiter structures outwardly sprung and to permit return of the outer ends to their undeflected condition in flexure tongue travel excursion limiting relation.
In this and like embodiments, typically, the flexure tongue has a proximate end fixed to the flexure and a distal end free of connection to the flexure, the pair of limiter structures being fixed to the flexure tongue right and left edges intermediate its the proximate and distal ends, the flexure tongue has a proximate end fixed to the flexure frame and a distal end free of connection to the flexure frame, the limiter structure being fixed to the flexure tongue at its the distal end, the load beam defining the offset opening relative to distal end fixed limiter structure, the flexure tongue further defines intermediate its proximate and distal ends a pair of limiter structures, the load beam defining a pair of further openings offset relative to the pair of limiter structures for passage of the pair of the limiter structures only in their deflected condition, and the distal end limiter structure is a first limiter structure, the intermediate limiter structures are second and third limiter structures and in which the flexure tongue further defines at its the proximate end a fourth the limiter structure, the load beam defining a further opening offset relative to the fourth limiter structure for passage of the fourth limiter structure only in its deflected condition.
In a further embodiment, the invention provides a flexure for a disk drive suspension comprising a frame and a cantilevered tongue, the tongue defining a normally upright, resilient tab extending at an angle of between 68 and 88 degrees relative to the flexure tongue and having a hook-shaped free end, the tab being adapted to snap-fit into an offset opening in an opposing load beam and return to its the upright condition in tongue travel limiting relation relative to the frame.
In this and like embodiments, typically, the tab is sized to extend through the load beam opening, the tab hook-shaped free end being sized to overlie in the tab upright condition an edge margin of the load beam opening in flexure excursion limiting relation.
In its method aspects the invention contemplates the method of assembling a suspension including juxtaposing a load beam and a flexure comprising a frame and tongue, carrying on the flexure tongue a limiter having an inner end attached to the flexure tongue and an outer end spaced from the inner end at a distance giving the limiter a predefined height, forming on the limiter outer end an enlarged head having a laterally extended portion to one side and having an inner edge opposed to the load beam, maintaining the limiter in a normally upright position at a predetermined angular orientation between 68 and 88 degrees, and preferably about 78 degrees, relative to the flexure tongue, defining a limiter enlarged head-passing opening in the load beam out of registration with the limiter in its the predetermined angular orientation and of a shape in the plane of the load beam generally congruent with the limiter enlarged head and laterally extended to one side, pressing the flexure and the load beam together at a spacing less than the limiter predefined height, deflecting the limiter from its predetermined angular orientation to a smaller angle relative to the flexure tongue, passing the limiter enlarged head through the load beam at the load beam opening and returning the tab to its normal upright position to selectively hook the limiter laterally extended portion with the edge margin of the load beam opening laterally extended portion in response to travel of the flexure tongue.